Face authentication techniques are known that analyze facial images captured by a camera and authenticate the individual (hereinbelow simply referred to as face authentication). In this kind of face authentication, there is the problem of unauthorized authentication in which someone else impersonates the individual by using a photograph of the individual. Moreover, various techniques are known for preventing unauthorized authentication by this kind of impersonation.
For example, Patent Document 1 discloses a technique for preventing unauthorized authentication by impersonation using a photograph or the like by performing a three-dimensional detection using multiple facial images of different orientations.